This invention relates to a method for processing residues of barium sulfide leaching or strontium sulfide leaching.
Barium sulfide leaching is a step in the process for producing barium compounds from the naturally occurring starting material, namely heavy spar (baryta). Heavy spar contains about 92 to 98% by weight of barium sulfate, varying amounts of calcium salts and iron salts, as well as silicate. Ground heavy spar is mixed with finely ground charcoal and reduced at high temperatures (approximately 1200.degree. C.) to barium sulfide. The cooled melt containing barium sulfide is extracted with hot water to form barium sulfide lye. The barium sulfide lye obtained by this barium sulfide leaching is an intermediate in the manufacture of many different organic and inorganic barium compounds. To form these compounds the lye is further reacted. For example, barium carbonate, which is used in the glass industry, can be prepared by introducing carbon dioxide.
Leaching of barium sulfide leaves a residue which contains mostly barium salts plus iron and calcium salts. The iron and calcium salts are especially in the form of the silicates and sulfides.
The preparation of strontium compounds is comparable to the preparation of barium compounds from barium sulfate. The starting material in this case is the naturally occurring mineral celestine, which consists primarily of strontium sulfate. The production of strontium compounds from this mineral is similar to the above-described production of barium compounds. The ground celestite is mixed with charcoal, reduced at high temperatures to strontium sulfide, and the cooled melt is extracted with hot water to form a strontium sulfide lye. This strontium sulfide lye obtained by leaching strontium sulfide is an intermediate in the preparation of a great number of strontium compounds. The far greatest part of this lye is further reacted to strontium carbonate, for example by introducing carbon dioxide. Strontium carbonate is used on a large scale in making television picture tubes. The leaching of strontium sulfide also leaves a residue.